Image sensors provide a grid of pixel unit cells for recording an intensity or brightness of incident light. In some applications, each pixel unit cell responds to the incident light by accumulating charge carriers (such as electrons and/or holes) generated when the incident light passes into/through a silicon layer. The greater intensity or brightness of the incident light, the more charge carriers are generated.
The charge carriers are received by a readout circuit and converted into an electrical signal subsequently usable by another circuit to provide color and/or brightness information for suitable applications, such as cameras. Light sensing elements and readout circuits are usable in a charge-coupled device (CCD), a complementary metal oxide semiconductor (CMOS) image sensor (CIS), an active-pixel sensor (APS), a passive-pixel sensor or other light detecting devices.